The brown long-eared bat or common long-eared bat (Plecotus auritus) is a fairly large European bat. It has distinctive ears, long and with a distinctive fold. It is extremely similar to the much rarer grey long-eared bat which was only validated as a distinct species in the 1960s.An adult brown long-eared bat has a body length of 4.5-4.8 cm, a tail of 4.1-4.6 cm, and a wing length of 4-4.2 cm.